Collagens are a family of proteins that strengthen and support connective tissues, such as the skin, tendons, ligaments, and bones. Collagen 7, as the major component of anchoring fibrils, functions in strengthening and stabilizing various tissues, including the skin (Ricard-Blum, Cold Spring Harb Perspect Biol 3(1):a004978 (2011)).
Collagen 7 is synthesized as three pro-α1(VII) polypeptide chains, which are subsequently processed and folded into a triple helical procollagen 7 protein in the endoplasmic reticulum. Procollagen 7 is secreted into the extracellular space, where it is further processed into mature collagen 7 (Chung et al. Dermatol Clin 28(1): 93-105 (2010)). Mature collagen 7 undergoes a multistep polymerization process to form the structural anchoring fibrils (Fritsch et al. J Biol Chem 284(44): 30248-30256 (2009)). In the skin, these anchoring fibrils are found in the epidermal basement membrane zone, which is the two-layer membrane located between the top layer of skin, the epidermis, and the underlying dermis. Here the anchoring fibrils connect the epidermal basement membrane to the papillary dermis. This connection aids in holding the epidermal and dermal layers of the skin together, providing structure and stability to the skin (Villone et al. J Biol Chem 283(36): 24506-24513 (2008)).